1. Field of the Invention
The present invention relates to a circuit regulator and a synchronous timing pulse generation circuit thereof, and more particularly to a circuit regulator and a synchronous timing pulse generation circuit thereof, capable of synchronously controlling a pulse starting time of a pulse-width-modulation signal, and preventing an inductor current from entering a Continuous Conduction Mode (CCM).
2. Related Art
Now, power supplies are not only required to provide stable output voltages and output currents for various electronic devices, but also required to satisfy the requirements of electronic devices on safety regulations. According to the design techniques, power supplies can be categorized into linear power supplies and switching power supplies. However, the linear power supply needs large and heavy isolation transformers and also large capacitors for regulation, which results in problems of larger volume and heavier weight. A worse part is that the linear power supply has excessively low conversion efficiency. Hence, at a practical application level, as compared with the linear power supply, a switching power supply formed by smaller power electronic switches, a lighter isolation transformer, a smaller capacitor, and a diode has better industrial applicability and is mostly used.
Generally, a working frequency of the switching power supply is between 20 KHz and 100 KHz. If it is used in cooperation with a Zero Voltage Switching (ZVS), a switching frequency can be further increased to be higher than 200 KHz, so as to obtain smaller and lighter design with higher power transfer efficiency and even high power factor in AC/DC applications.
However, the switching power supply has more complex operation modes. While an unexpected operation happens, the circuit may enter an unexpected operation mode and let the converter fail to keep output current constant. For example, FIG. 1 is a brief circuit architecture view of a conventional switching power supply. When the switching power supply transfers the power from a primary side to a secondary side by performing the charging and discharging processes of magnetic core of the isolation transformer through the magnetic inductor L, the switching power supply generates a primary side switching current Ip and a secondary side switching current Is respectively at two sides of the transformer. When the primary side switching current Ip enters a CCM on the inductor L under improper control, it is very easy to result in successive accumulation of the inductor current in the charging and discharging processes of the transformer, so as to cause a problem of magnetic core saturation. In this situation, the core power loss will increase. This may also cause high switching current and higher switching loss of switching transistor and diodes. Consequently, additional power consumption of the switching power supply will be cost. Particularly, it is more difficult for the converter using primary side control to obtain an accurate and stable constant output current when undergoing the CCM.